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publishing docs for 0.13.1
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db
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0.13.1
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<li class="parent open current" data-id="db/DB" data-name="db">
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<ul>
<li class=" " data-id="db/DB/Any" data-name="db::any">
<a href="DB/Any.html">Any</a>
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<li class=" " data-id="db/DB/BeginTransaction" data-name="db::begintransaction">
<a href="DB/BeginTransaction.html">BeginTransaction</a>
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<a href="DB/Connection.html">Connection</a>
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<a href="DB/Driver.html">Driver</a>
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<a href="DB/DriverSpecs.html">DriverSpecs</a>
<ul>
<li class=" " data-id="db/DB/DriverSpecs/ColumnDef" data-name="db::driverspecs::columndef">
<a href="DB/DriverSpecs/ColumnDef.html">ColumnDef</a>
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<a href="DB/Field.html">Field</a>
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<a href="DB/Mappable.html">Mappable</a>
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<a href="DB/MappingException.html">MappingException</a>
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<a href="DB/MetadataValueConverter.html">MetadataValueConverter</a>
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<a href="DB/NoResultsError.html">NoResultsError</a>
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<a href="DB/Pool.html">Pool</a>
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<a href="DB/PoolPreparedStatement.html">PoolPreparedStatement</a>
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<a href="DB/PoolResourceLost.html">PoolResourceLost</a>
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<a href="DB/PoolStatement.html">PoolStatement</a>
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<a href="DB/PoolTimeout.html">PoolTimeout</a>
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<ul>
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<a href="DB/SessionMethods/UnpreparedQuery.html">UnpreparedQuery</a>
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<a href="DB/TopLevelTransaction.html">TopLevelTransaction</a>
</li>
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<a href="DB/Transaction.html">Transaction</a>
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</ul>
</li>
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<a href="Enum.html">Enum</a>
</li>
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</div>
</div>
<div class="main-content">
<h1 class="type-name">
<span class="kind">module</span> DB
</h1>
<h2>
<a id="overview" class="anchor" href="#overview">
<svg class="octicon-link" aria-hidden="true">
<use href="#octicon-link"/>
</svg>
</a>
Overview
</h2>
<p>The DB module is a unified interface for database access.
Individual database systems are supported by specific database driver shards.</p>
<p>Available drivers include:</p>
<ul>
<li><a href="https://github.com/crystal-lang/crystal-sqlite3">crystal-lang/crystal-sqlite3</a> for SQLite</li>
<li><a href="https://github.com/crystal-lang/crystal-mysql">crystal-lang/crystal-mysql</a> for MySQL and MariaDB</li>
<li><a href="https://github.com/will/crystal-pg">will/crystal-pg</a> for PostgreSQL</li>
<li><a href="https://github.com/kaukas/crystal-cassandra">kaukas/crystal-cassandra</a> for Cassandra</li>
</ul>
<p>For basic instructions on implementing a new database driver, check <code><a href="DB/Driver.html">Driver</a></code> and the existing drivers.</p>
<p>DB manages a connection pool. The connection pool can be configured by query parameters to the
connection <code>URI</code> as described in <code><a href="DB/Database.html">Database</a></code>.</p>
<h3><a id="usage" class="anchor" href="#usage">
<svg class="octicon-link" aria-hidden="true">
<use href="#octicon-link"/>
</svg>
</a>Usage</h3>
<p>Assuming <code>crystal-sqlite3</code> is included a SQLite3 database can be opened with <code><a href="DB.html#open%28uri%3AURI%7CString%29-class-method">#open</a></code>.</p>
<pre><code class="language-crystal">db <span class="o">=</span> <span class="t">DB</span>.open <span class="s">&quot;sqlite3:./path/to/db/file.db&quot;</span>
db.close</code></pre>
<p>If a block is given to <code><a href="DB.html#open%28uri%3AURI%7CString%29-class-method">#open</a></code> the database is closed automatically</p>
<pre><code class="language-crystal"><span class="t">DB</span>.open <span class="s">&quot;sqlite3:./file.db&quot;</span> <span class="k">do</span> <span class="o">|</span>db<span class="o">|</span>
<span class="c"># work with db</span>
<span class="k">end</span> <span class="c"># db is closed</span></code></pre>
<p>In the code above <code>db</code> is a <code><a href="DB/Database.html">Database</a></code>. Methods available for querying it are described in <code><a href="DB/QueryMethods.html">QueryMethods</a></code>.</p>
<p>Three kind of statements can be performed:</p>
<ol>
<li><code>Database#exec</code> waits no response from the database.</li>
<li><code>Database#scalar</code> reads a single value of the response.</li>
<li><code>Database#query</code> returns a ResultSet that allows iteration over the rows in the response and column information.</li>
</ol>
<p>All of the above methods allows parametrised query. Either positional or named arguments.</p>
<p>Check a full working version:</p>
<p>The following example uses SQLite where <code>?</code> indicates the arguments. If PostgreSQL is used <code>$1</code>, <code>$2</code>, etc. should be used. <code>crystal-db</code> does not interpret the statements.</p>
<pre><code class="language-crystal"><span class="k">require</span> <span class="s">&quot;db&quot;</span>
<span class="k">require</span> <span class="s">&quot;sqlite3&quot;</span>
<span class="t">DB</span>.open <span class="s">&quot;sqlite3:./file.db&quot;</span> <span class="k">do</span> <span class="o">|</span>db<span class="o">|</span>
<span class="c"># When using the pg driver, use $1, $2, etc. instead of ?</span>
db.exec <span class="s">&quot;create table contacts (name text, age integer)&quot;</span>
db.exec <span class="s">&quot;insert into contacts values (?, ?)&quot;</span>, <span class="s">&quot;John Doe&quot;</span>, <span class="n">30</span>
args <span class="o">=</span> <span class="o">[]</span> <span class="k">of</span> <span class="t">DB</span><span class="t">::</span><span class="t">Any</span>
args <span class="o">&lt;&lt;</span> <span class="s">&quot;Sarah&quot;</span>
args <span class="o">&lt;&lt;</span> <span class="n">33</span>
db.exec <span class="s">&quot;insert into contacts values (?, ?)&quot;</span>, args: args
puts <span class="s">&quot;max age:&quot;</span>
puts db.scalar <span class="s">&quot;select max(age) from contacts&quot;</span> <span class="c"># =&gt; 33</span>
puts <span class="s">&quot;contacts:&quot;</span>
db.query <span class="s">&quot;select name, age from contacts order by age desc&quot;</span> <span class="k">do</span> <span class="o">|</span>rs<span class="o">|</span>
puts <span class="s">&quot;</span><span class="i">#{</span>rs.column_name(<span class="n">0</span>)<span class="i">}</span><span class="s"> (</span><span class="i">#{</span>rs.column_name(<span class="n">1</span>)<span class="i">}</span><span class="s">)&quot;</span>
<span class="c"># =&gt; name (age)</span>
rs.each <span class="k">do</span>
puts <span class="s">&quot;</span><span class="i">#{</span>rs.read(<span class="t">String</span>)<span class="i">}</span><span class="s"> (</span><span class="i">#{</span>rs.read(<span class="t">Int32</span>)<span class="i">}</span><span class="s">)&quot;</span>
<span class="c"># =&gt; Sarah (33)</span>
<span class="c"># =&gt; John Doe (30)</span>
<span class="k">end</span>
<span class="k">end</span>
<span class="k">end</span></code></pre>
<h3><a id="object-mapping" class="anchor" href="#object-mapping">
<svg class="octicon-link" aria-hidden="true">
<use href="#octicon-link"/>
</svg>
</a>Object mapping</h3>
<p>The <code><a href="DB/Serializable.html">DB::Serializable</a></code> module implements a declarative mapping from DB result
sets to Crystal types.</p>
<h2>
<a id="defined-in" class="anchor" href="#defined-in">
<svg class="octicon-link" aria-hidden="true">
<use href="#octicon-link"/>
</svg>
</a>
Defined in:
</h2>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db.cr#L82" target="_blank">
db.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/begin_transaction.cr#L1" target="_blank">
db/begin_transaction.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/connection.cr#L1" target="_blank">
db/connection.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/connection_builder.cr#L1" target="_blank">
db/connection_builder.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/connection_context.cr#L1" target="_blank">
db/connection_context.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/database.cr#L4" target="_blank">
db/database.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/disposable.cr#L1" target="_blank">
db/disposable.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/driver.cr#L1" target="_blank">
db/driver.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/enumerable_concat.cr#L1" target="_blank">
db/enumerable_concat.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/error.cr#L1" target="_blank">
db/error.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/mapping.cr#L1" target="_blank">
db/mapping.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/pool.cr#L5" target="_blank">
db/pool.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/pool_prepared_statement.cr#L1" target="_blank">
db/pool_prepared_statement.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/pool_statement.cr#L1" target="_blank">
db/pool_statement.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/pool_unprepared_statement.cr#L1" target="_blank">
db/pool_unprepared_statement.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/query_methods.cr#L1" target="_blank">
db/query_methods.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/result_set.cr#L1" target="_blank">
db/result_set.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/serializable.cr#L1" target="_blank">
db/serializable.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/session_methods.cr#L1" target="_blank">
db/session_methods.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/statement.cr#L1" target="_blank">
db/statement.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/string_key_cache.cr#L1" target="_blank">
db/string_key_cache.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/transaction.cr#L1" target="_blank">
db/transaction.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/version.cr#L1" target="_blank">
db/version.cr
</a>
<br/>
<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/spec.cr#L9" target="_blank">
spec.cr
</a>
<br/>
<h2>
<a id="constant-summary" class="anchor" href="#constant-summary">
<svg class="octicon-link" aria-hidden="true">
<use href="#octicon-link"/>
</svg>
</a>
Constant Summary
</h2>
<dl>
<dt class="entry-const" id="Log">
<strong>Log</strong> = <code><span class="t">::</span><span class="t">Log</span>.<span class="k">for</span>(<span class="k">self</span>)</code>
</dt>
<dt class="entry-const" id="TYPES">
<strong>TYPES</strong> = <code>[<span class="t">Nil</span>, <span class="t">String</span>, <span class="t">Bool</span>, <span class="t">Int32</span>, <span class="t">Int64</span>, <span class="t">Float32</span>, <span class="t">Float64</span>, <span class="t">Time</span>, <span class="t">Bytes</span>]</code>
</dt>
<dd class="entry-const-doc">
<p>Types supported to interface with database driver.
These can be used in any <code><a href="DB/ResultSet.html#read-instance-method">ResultSet#read</a></code> or any <code>Database#query</code> related
method to be used as query parameters</p>
</dd>
<dt class="entry-const" id="VERSION">
<strong>VERSION</strong> = <code><span class="s">&quot;0.13.1&quot;</span></code>
</dt>
</dl>
<h2>
<a id="class-method-summary" class="anchor" href="#class-method-summary">
<svg class="octicon-link" aria-hidden="true">
<use href="#octicon-link"/>
</svg>
</a>
Class Method Summary
</h2>
<ul class="list-summary">
<li class="entry-summary">
<a href="#connect%28uri%3AURI%7CString%29-class-method" class="signature"><strong>.connect</strong>(uri : URI | String)</a>
<div class="summary"><p>Opens a connection using the specified <em>uri</em>.</p></div>
</li>
<li class="entry-summary">
<a href="#connect%28uri%3AURI%7CString%2C%26%29-class-method" class="signature"><strong>.connect</strong>(uri : URI | String, &)</a>
<div class="summary"><p>Opens a connection using the specified <em>uri</em>.</p></div>
</li>
<li class="entry-summary">
<a href="#open%28uri%3AURI%7CString%29-class-method" class="signature"><strong>.open</strong>(uri : URI | String)</a>
<div class="summary"><p>Creates a <code><a href="DB/Database.html">Database</a></code> pool and opens initial connection(s) as specified in the connection <em>uri</em>.</p></div>
</li>
<li class="entry-summary">
<a href="#open%28uri%3AURI%7CString%2C%26%29-class-method" class="signature"><strong>.open</strong>(uri : URI | String, &)</a>
<div class="summary"><p>Same as <code><a href="DB.html#open%28uri%3AURI%7CString%29-class-method">#open</a></code> but the database is yielded and closed automatically at the end of the block.</p></div>
</li>
<li class="entry-summary">
<a href="#register_driver%28driver_name%2Cdriver_class%3ADriver.class%29-class-method" class="signature"><strong>.register_driver</strong>(driver_name, driver_class : <span class="t">Driver</span>.<span class="k">class</span>)</a>
<div class="summary"><p>Registers a driver class for a given <em>driver_name</em>.</p></div>
</li>
</ul>
<h2>
<a id="macro-summary" class="anchor" href="#macro-summary">
<svg class="octicon-link" aria-hidden="true">
<use href="#octicon-link"/>
</svg>
</a>
Macro Summary
</h2>
<ul class="list-summary">
<li class="entry-summary">
<a href="#mapping%28properties%2Cstrict%3Dtrue%29-macro" class="signature"><strong>mapping</strong>(properties, strict = <span class="n">true</span>)</a>
<div class="summary"><p>The <code><a href="DB.html#mapping%28%2A%2Aproperties%29-macro">DB.mapping</a></code> macro defines how an object is built from a <code><a href="DB/ResultSet.html">ResultSet</a></code>.</p>
<p><span class="flag red">DEPRECATED</span> Use <code><a href="DB/Serializable.html">DB::Serializable</a></code> instead</p></div>
</li>
<li class="entry-summary">
<a href="#mapping%28%2A%2Aproperties%29-macro" class="signature"><strong>mapping</strong>(**properties)</a>
<div class="summary"><p><span class="flag red">DEPRECATED</span> Use <code><a href="DB/Serializable.html">DB::Serializable</a></code> instead</p></div>
</li>
</ul>
<div class="methods-inherited">
</div>
<h2>
<a id="class-method-detail" class="anchor" href="#class-method-detail">
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Class Method Detail
</h2>
<div class="entry-detail" id="connect(uri:URI|String)-class-method">
<div class="signature">
def self.<strong>connect</strong>(uri : URI | String)
<a class="method-permalink" href="#connect%28uri%3AURI%7CString%29-class-method">#</a>
</div>
<div class="doc">
<p>Opens a connection using the specified <em>uri</em>.
The scheme of the <em>uri</em> determines the driver to use.
Returned connection must be closed by <code>Connection#close</code>.
If a block is used the connection is yielded and closed automatically.</p>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db.cr#L140" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="connect(uri:URI|String,&amp;)-class-method">
<div class="signature">
def self.<strong>connect</strong>(uri : URI | String, &)
<a class="method-permalink" href="#connect%28uri%3AURI%7CString%2C%26%29-class-method">#</a>
</div>
<div class="doc">
<p>Opens a connection using the specified <em>uri</em>.
The scheme of the <em>uri</em> determines the driver to use.
Returned connection must be closed by <code>Connection#close</code>.
If a block is used the connection is yielded and closed automatically.</p>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db.cr#L145" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="open(uri:URI|String)-class-method">
<div class="signature">
def self.<strong>open</strong>(uri : URI | String)
<a class="method-permalink" href="#open%28uri%3AURI%7CString%29-class-method">#</a>
</div>
<div class="doc">
<p>Creates a <code><a href="DB/Database.html">Database</a></code> pool and opens initial connection(s) as specified in the connection <em>uri</em>.
Use <code><a href="DB.html#connect%28uri%3AURI%7CString%29-class-method">DB#connect</a></code> to open a single connection.</p>
<p>The scheme of the <em>uri</em> determines the driver to use.
Connection parameters such as hostname, user, database name, etc. are specified according
to each database driver's specific format.</p>
<p>The returned database must be closed by <code><a href="DB/Database.html#close-instance-method">Database#close</a></code>.</p>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db.cr#L122" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="open(uri:URI|String,&amp;)-class-method">
<div class="signature">
def self.<strong>open</strong>(uri : URI | String, &)
<a class="method-permalink" href="#open%28uri%3AURI%7CString%2C%26%29-class-method">#</a>
</div>
<div class="doc">
<p>Same as <code><a href="DB.html#open%28uri%3AURI%7CString%29-class-method">#open</a></code> but the database is yielded and closed automatically at the end of the block.</p>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db.cr#L127" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="register_driver(driver_name,driver_class:Driver.class)-class-method">
<div class="signature">
def self.<strong>register_driver</strong>(driver_name, driver_class : <span class="t">Driver</span>.<span class="k">class</span>)
<a class="method-permalink" href="#register_driver%28driver_name%2Cdriver_class%3ADriver.class%29-class-method">#</a>
</div>
<div class="doc">
<p>Registers a driver class for a given <em>driver_name</em>.
Should be called by drivers implementors only.</p>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db.cr#L106" target="_blank">View source</a>]
</div>
</div>
<h2>
<a id="macro-detail" class="anchor" href="#macro-detail">
<svg class="octicon-link" aria-hidden="true">
<use href="#octicon-link"/>
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Macro Detail
</h2>
<div class="entry-detail" id="mapping(properties,strict=true)-macro">
<div class="signature">
macro <strong>mapping</strong>(properties, strict = <span class="n">true</span>)
<a class="method-permalink" href="#mapping%28properties%2Cstrict%3Dtrue%29-macro">#</a>
</div>
<div class="doc">
<p>The <code><a href="DB.html#mapping%28%2A%2Aproperties%29-macro">DB.mapping</a></code> macro defines how an object is built from a <code><a href="DB/ResultSet.html">ResultSet</a></code>.</p>
<p>It takes hash literal as argument, in which attributes and types are defined.
Once defined, <code><a href="DB/ResultSet.html#read%28type%3AEnum.class%29-instance-method">ResultSet#read(t)</a></code> populates properties of the class from the
<code><a href="DB/ResultSet.html">ResultSet</a></code>.</p>
<pre><code class="language-crystal"><span class="k">require</span> <span class="s">&quot;db&quot;</span>
<span class="k">class</span> <span class="t">Employee</span>
<span class="t">DB</span>.mapping({
title: <span class="t">String</span>,
name: <span class="t">String</span>,
})
<span class="k">end</span>
employees <span class="o">=</span> <span class="t">Employee</span>.from_rs(db.query(<span class="s">&quot;SELECT title, name FROM employees&quot;</span>))
employees[<span class="n">0</span>].title <span class="c"># =&gt; &quot;Manager&quot;</span>
employees[<span class="n">0</span>].name <span class="c"># =&gt; &quot;John&quot;</span></code></pre>
<p>Attributes not mapped with <code><a href="DB.html#mapping%28%2A%2Aproperties%29-macro">DB.mapping</a></code> are not defined as properties.
Also, missing attributes raise a <code><a href="DB/MappingException.html">DB::MappingException</a></code>.</p>
<p>You can also define attributes for each property.</p>
<pre><code class="language-crystal"><span class="k">class</span> <span class="t">Employee</span>
<span class="t">DB</span>.mapping({
title: <span class="t">String</span>,
name: {
<span class="k">type</span>: <span class="t">String</span>,
nilable: <span class="n">true</span>,
key: <span class="s">&quot;firstname&quot;</span>,
},
})
<span class="k">end</span></code></pre>
<p>Available attributes:</p>
<ul>
<li><em>type</em> (required) defines its type. In the example above, <em>title: String</em> is a shortcut to <em>title: {type: String}</em>.</li>
<li><em>nilable</em> defines if a property can be a <code>Nil</code>.</li>
<li><strong>default</strong>: value to use if the property is missing in the result set, or if it's <code>null</code> and <code>nilable</code> was not set to <code>true</code>. If the default value creates a new instance of an object (for example <code>[1, 2, 3]</code> or <code>SomeObject.new</code>), a different instance will be used each time a row is parsed.</li>
<li><em>key</em> defines which column to read from a <code><a href="DB/ResultSet.html">ResultSet</a></code>. It defaults to the name of the property.</li>
<li><em>converter</em> takes an alternate type for parsing. It requires a <code>#from_rs</code> method in that class, and returns an instance of the given type.</li>
</ul>
<p>The mapping also automatically defines Crystal properties (getters and setters) for each
of the keys. It doesn't define a constructor accepting those arguments, but you can provide
an overload.</p>
<p>The macro basically defines a constructor accepting a <code><a href="DB/ResultSet.html">ResultSet</a></code> that reads from
it and initializes this type's instance variables.</p>
<p>This macro also declares instance variables of the types given in the mapping.</p>
<p><span class="flag red">DEPRECATED</span> Use <code><a href="DB/Serializable.html">DB::Serializable</a></code> instead</p>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/mapping.cr#L62" target="_blank">View source</a>]
</div>
</div>
<div class="entry-detail" id="mapping(**properties)-macro">
<div class="signature">
macro <strong>mapping</strong>(**properties)
<a class="method-permalink" href="#mapping%28%2A%2Aproperties%29-macro">#</a>
</div>
<div class="doc">
<p><span class="flag red">DEPRECATED</span> Use <code><a href="DB/Serializable.html">DB::Serializable</a></code> instead</p>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-lang/crystal-db/blob/v0.13.1/src/db/mapping.cr#L154" target="_blank">View source</a>]
</div>
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